Preparation of nu-substituted aminophenols



Patented F b. 12, 1.946

mamas ON or N-SUBSTITUTED AMINOPHENOLS Frederic Rochester, N. Y;assignor to v Eastman Kodak Company, Bochester N. Y., a corporation ofNew Jersey No Drawing. Application July 22, 19 12,

' Serial No. 451.894

'1 Claims. (01. 204- 14) This invention relates to a process forpreparing Nesubstituted aminophenols of the typeoiN-aralkylaminophenols.

N-aralkylaminophenolsp such as N-benzyl-paminophenol, and N furiuryl-paminophenol, have been prepared by the'alkali-zinc dust or thealkali-aluminium reduction of N-benzylidene-paminophenol andN-furfurylidene-p-aminophe- The following example will serve toillustrate the manner of practicing-the invention.- I

Example 1.N-furfuryl-p-aminophenol 18.6 g. ofN-furiurylidene-p-aminophenol were dissolved in 400 cc. of'an aqueoussolution of nol. N -benzyl'-p-aminophenol has also been prepared byreducing N-benzylidene-p-aminophenol electrolytically, using an aqueousalcoholicsolution of sodium acetate as a combined electrolyte andsolvent-the water and sodium acetate serving as the electrolyte and thealcohol as the solvent for the N-benzylidene-p-aminophenol. A

lead cathode wasemployed. This electrolytic method requires a fairlyhightemperature (about 80 C.) for its successful operation. At suchtemperatures, under the alkaline conditions imposed by the sodiumacetate electrolyte, the N-benzylp-aminophenol which is formed iscontaminated with decomposition products. Moreover, in order to isolatethe N-benzyl-p-ami'nophenol, it is necessary to remove the alcohol,and'ifor practical .operation the alcohol should be recovered.

I have now found that N.-'ara1ky lidene aminophenols can be reducedelectrolytically to N- aralkylaminophenols, using aqueous alkali as thecombined electrolyte and solvent. Especially when a dilute alkalisolution (e. g. about 1 percent NaOH)- is used, the reduction proceedsat a lower temperature and at a lower average pofrom the solution);

sodium hydroxide containing 1 percent by weight of sodium hydroxide. Theresulting solution was placed in the cathode compartment of an-elec-'trolytic cell. The cathode was composed 01- a cylindrical zinc sheet andseparated from the anode by means of a porous diaphragm. The anodeconsisted of a cylindrical sheet of nickel. The anolyte was also a 1percent aqueou sodium hydroxidesolution. The reduction was then'run at25 C. at a current density of 0.01 ampere per square centimeter atapotential of 5 volts. The reduction proceeded smoothly and a iaintlyyel-' lowed or straw-colored solution was obtained after completion ofthe ,reduction (which was evident from the hydrogen which began toevolve N-furfuryl-p-aminophenoi was precipitated as a white solid whensodium bisulflte' was added to the yellowish solution. It

was filtered oil and then washed with water and dried. It melted at 110to 111 1C. Its nitr derivative melted at 95 to 98 C.

Example 2.N-benzul-p-aminophenol 5 g. oi N-benzylidene-p-aminophenolwere dis- J solved in 400 cc. of an aqueous solution of sodium tentialthan when aqueous alcoholic sodium acetate is used as the electrolyte,with the result that the N-aralkyl-aminophenols are obtained relativelyfree from decomposition products. N-

alkylaminophenols cannot be made by my new process.

Itis accordingly an object oi! my invention to provide an improvedproces for preparing N- aralkylaminophenols. Other objects willbecomeapparent hereinafter.

In accordancewith the invention, N aralkylidene aminophenols, e. g.N-benzylidene-p-aminophenol, and N-furfurylidene-p-aminophenol, arereduced electrolytically, using an aqueous solution of an alkali metalhydroxide as the electro-- lyte. Advantageously, a diluteaqueoussolutionof sodium hydroxide is employed. When the con-' centration ofthe alkali is low, i. e. of the order of 1 percent, the reductionproceeds at relatively low temperatures and relatively low averagepotentials, thereby considerably minimizing any deterioration of theN-aralkylideneaminophenols or the N-aralkylaminophenols which areformed.

hydroxide containing 1 percent by weight of so- The resulting solutionwas dium hydroxide. placed in the cathode compartment or an elec-'vtrolytie cell.' The cathode was composed oi a cylindrical zilic sheetand separated from the anode by a Coors porous clay diaphragm. The

anode consisted of a cylindrical sheet of nickel.

The anoiyte cdnsistedoi an aqueous solution containing 1 percent byweight of sodium hydroxide and 10 percent by'weight of sodium sulfate.The

reduction was then run at 25 C. at a current density of between 0.0033and 0.0066 amperes per square centimeter at a potential of from 3.2 to3.7 volts. At the end of two hours, the catholyte was acidified withhydrochloric acid and chariiltered hot. Upon cooling white crystals 0!N- benzyl-p-aminophenol hydrochloride separated out. The crystals meltedat 171 to 172 C. The crystals were dissolved in water and treated withsodium bicarbonate, whereupon N-benzyl-p-' aminophenol-separated out. Itmelted at 88' to 8 9 0.. The sodium sulfate was employed in the anolyteabove to retard pumping" of the anolyte into the catholyte. Thereduction is also advantageously begun with catholyte liquid-at a higherlevel than the anolyte liquid, in order to overcome pumping."

In a manner similar to thatillustrated in the foregoing examples, N-(4-methylbenzylidene) -pamlnophenol, N- (4-methoxy zyl) -p-aminopheno],and other N-aralkylidene aminophenols canbe reduced.. v.

What I claim. as my invention and desire to be secured by Letters Patentof the United Statesis:

1. In a process for electrolytically reducing a compound selected fromthe group consisting of N-aralkylldene-p-aminophenols and N-furfuryli--dene-p-aminophenol to produce 'N-aralkyl-paminophenols andN-furfuryl-p-aminophenol in a diaphragm containing electrolytic cell,-the' im- .2. "assess? M of sodium hydroxide and a N-aralkylidene p'am'inophenol. Y

4. In a process for electrolytically reducing N-benzylidene-p-aminophenol to N-benzyl-p ami-fl nophenol in adiaphragm-containing electrolytic cell, the improvement which comprisesemploy-g ing 'atemperature of not more than about C; a zinc cathode anda catholyte comprising a water solution of an alkali metal hydroxide contaming about one percent by-weight of the alkali metal hydroxide andN-benzylidene-p-amino- I phenol.

- provement which comprises employing a temperature of not more thanabout 25 0., a zinc cathode. and a catholyte comprising essentially awater solution of an alkali metal'hydroxlde containingabout one percentby weight of the alkali metal hydroxide and a compound selected from thegroup consisting of a N-aralkylidene-paminophenol andN-furiurylidene-p-aminophenol.

2. In a processfor electrolytically reducing aN-aralkylidene-p-aminophenol to produce a N- aralkyl-p-aminophenol' in adiaphragmecontaine ing electrolytic cells the improvement whichcomaralkyl-p-aminophenol in-a, diaphragm-containing electrolytic cell,the improvement which comprises employing a temperature of not more than.about 25 0., a zinc .cathode and a catholyte comprising essentially awater solution of sodium hydroxide containing about one percent byweight .5. In a process for electrolytically reducing l I-'benzylidene-p arninophenol to-N-benZyI-p-ami- .nophenol'in adiaphragm-containing electrolytic cell, the improvement whichcomprisesemploy--v ing a temperature of not-more than about 25 Cl,

a zinc cathode and a catholyte comprising a water solution of-sodiumhydroxide containing about one percentbrweight of sodium hydroxide andN-benzylidene-p-aminophenol. p

6. In a process for electrolytically reducing N-furfurylidene-p-aminophenol to N -furfuryl-.-paminophenol in adiaphragm-containing electrolytic cell, the improvement which comprisesemploying a temperature'of not more than-about 25 C., a zinccathode anda catholyte comprising a water solution of an alkali'm'etalhydroxide containing about one percent by weight of the alkali Naralkylidene-p-aminophenol to produce aN- metal hydroxide andN-furiurylidene-p-aminophenol.

. 'l.-1n a process for electrolytically reducingNfurfurylidene-p-aminophenol to. II-furtun'rl-p-v aminophenol in adiaphragm containing electro lytic cell, the improvement which comprisesemploying a temperature'of not. more than about C., a zinc cathode and acatholyte compri'sing a water solution of sodium hydroxide con--taming-about one percent by weight of the alkali metalhydroxide and'N-i'urfurylidene-p aminoa phenoh "FREDERIC R. BEAN. 5

